Hot melt pressure sensitive adhesive composition and pressure sensitive adhesive sheet

Abstract

To provide a hot-melt type adhesive composition which has low viscosity on melting by heating and with which an adhesive layer can suitably be formed.SOLUTION: According to the application, a hot-melt type adhesive composition containing a base polymer is provided. The base polymer contains an acrylic polymer A and an acrylic polymer B. Here, the acrylic polymer A is a polymer of a monomer component of which the main constituent is a (meth)acrylic monomer A having a 4-8C alkyl group, and the acrylic polymer B is a polymer of a monomer component of which the main constituent is a (meth)acrylic monomer B having a 9-12C alkyl group. A content of the acrylic polymer B in the base polymer is 10-90 wt.% based on 100 wt.% of the sum total of the acrylic polymer A and the acrylic polymer B.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hot melt pressure-sensitive adhesive composition. The present invention also relates to a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the hot melt pressure-sensitive adhesive composition. [Background technology]

[0002] Generally, adhesives (also called pressure-sensitive adhesives; the same applies below) are soft and solid (viscoelastic) at temperatures around room temperature, and have the property of easily adhering to an adherend when pressure is applied. Taking advantage of these properties, adhesives are widely used in various industrial fields, from home appliances to automobiles and office equipment, as a joining method that is easy to work with and has high adhesive reliability.

[0003] Typically, a pressure-sensitive adhesive is formed into a film using a pressure-sensitive adhesive composition, and used in the form of a pressure-sensitive adhesive sheet containing the film-like pressure-sensitive adhesive (pressure-sensitive adhesive layer). In the production of a pressure-sensitive adhesive sheet of this configuration, a pressure-sensitive adhesive composition in the form of a solvent solution such as a toluene solution is generally used, and the solvent solution is applied to a suitable surface to form a pressure-sensitive adhesive layer. However, in recent years, there has been a demand for reduced solvent use to protect the environment, and the use of solvent-free hot-melt pressure-sensitive adhesive compositions in the formation of pressure-sensitive adhesive layers has also been considered. Patent Document 1 is an example of a technical document relating to this type of hot-melt pressure-sensitive adhesive composition. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-147655 Summary of the Invention [Problem to be solved by the invention]

[0005] A hot-melt pressure-sensitive adhesive composition is typically extruded in a heated and molten state through the die of an extruder to form a film, thereby forming a pressure-sensitive adhesive layer. If the viscosity of the molten hot-melt pressure-sensitive adhesive composition is too high, it becomes difficult to extrude the pressure-sensitive adhesive composition through the die, which can lead to a decrease in the thickness uniformity of the pressure-sensitive adhesive layer and, in turn, to a poor appearance of the pressure-sensitive adhesive sheet. In particular, from the viewpoint of adhesive properties, when a high-molecular-weight polymer is used as the base polymer contained in the hot-melt pressure-sensitive adhesive composition, the viscosity of the pressure-sensitive adhesive composition tends to be high. Therefore, it would be beneficial to obtain a hot-melt pressure-sensitive adhesive composition whose viscosity in the molten state is low enough to be suitable for application to extrusion molding.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hot melt pressure-sensitive adhesive composition that has a low viscosity in a molten state and can suitably form a pressure-sensitive adhesive layer. Another object of the present invention is to provide a pressure-sensitive adhesive sheet obtained using the hot melt pressure-sensitive adhesive composition. [Means for solving the problem]

[0007] According to this specification, there is provided a hot melt pressure-sensitive adhesive composition containing a base polymer. The base polymer contains an acrylic polymer A and an acrylic polymer B. Here, the acrylic polymer A is a polymer of monomer components mainly composed of a (meth)acrylic monomer A having an alkyl group with 4 to 8 carbon atoms. The acrylic polymer B is a polymer of monomer components mainly composed of a (meth)acrylic monomer B having an alkyl group with 9 to 12 carbon atoms. When the total amount of the acrylic polymer A and the acrylic polymer B in the base polymer is taken as 100% by weight, the content of the acrylic polymer B is 10% by weight or more and 90% by weight or less.

[0008] Such a hot melt pressure-sensitive adhesive composition has a suitably low viscosity when heated and melted, and can therefore be suitably used in, for example, extrusion molding to form a pressure-sensitive adhesive layer.

[0009] In a preferred embodiment, the (meth)acrylic monomer A is an alkyl(meth)acrylate having an alkyl group having from 4 to 8 carbon atoms at the ester terminal. In another preferred embodiment, the (meth)acrylic monomer B is an alkyl(meth)acrylate having an alkyl group having from 9 to 12 carbon atoms at the ester terminal. A pressure-sensitive adhesive composition containing, as base polymers, acrylic polymer A and acrylic polymer B, which are polymers of monomer components having these monomers as main components, can easily achieve both improved adhesive properties (e.g., adhesive strength and holding power) and low viscosity in a molten state.

[0010] In a preferred embodiment of the technology disclosed herein, the weight average molecular weight (Mw) of the acrylic polymer A is 75×10 4 Over 120 x 10 4 In another preferred embodiment of the technology disclosed herein, the weight average molecular weight (Mw) of the acrylic polymer B is 75×10 or less. 4 Over 120 x 10 4 The following is a summary of the results. Generally, when the Mw of the base polymer contained in a hot-melt pressure-sensitive adhesive composition is high, the viscosity of the pressure-sensitive adhesive composition in a molten state tends to be high, which can lead to failure to suitably form a pressure-sensitive adhesive layer by extrusion molding in a molten state, reduction in thickness uniformity of the formed pressure-sensitive adhesive layer, and poor appearance. According to the present invention, the viscosity of the pressure-sensitive adhesive composition when heated and melted is suitably low. Therefore, even in a pressure-sensitive adhesive composition in which the Mw of the acrylic polymer A and the acrylic polymer B contained in the base polymer are each equal to or greater than the above-mentioned predetermined value, the viscosity of the pressure-sensitive adhesive composition in a molten state is suitably low, making it easy to suitably form a pressure-sensitive adhesive layer. Furthermore, from the viewpoint of adhesive properties, it is preferable that the Mw of the acrylic polymer A and the acrylic polymer B is each equal to or less than the above-mentioned upper limit.

[0011] In a preferred embodiment of the technology disclosed herein, the hot-melt pressure-sensitive adhesive composition has a shear viscosity of 7000 Pa s or less at 130°C. A hot-melt pressure-sensitive adhesive composition having a shear viscosity of 7000 Pa s or less at 130°C tends to have a viscosity in a molten state that is easily suitable for extrusion molding, and therefore a pressure-sensitive adhesive layer can be easily formed.

[0012] In a preferred embodiment of the technology disclosed herein, the hot-melt pressure-sensitive adhesive composition further contains a crosslinking agent. Such a hot-melt pressure-sensitive adhesive composition tends to be able to form a pressure-sensitive adhesive layer with excellent adhesive properties due to suitably adjusted cohesive strength. In a preferred embodiment, the crosslinking agent is an isocyanate-based crosslinking agent.

[0013] According to this specification, a pressure-sensitive adhesive sheet is provided having a pressure-sensitive adhesive layer formed from any of the pressure-sensitive adhesive compositions disclosed herein. This configuration makes it easy to obtain a pressure-sensitive adhesive sheet that has good adhesive properties (e.g., adhesive strength and holding power) while having improved thickness uniformity and appearance. Furthermore, a pressure-sensitive adhesive sheet having this configuration is likely to be solvent-free, reducing the environmental burden.

[0014] In addition, any suitable combination of the above elements may also be included in the scope of the invention for which patent protection is sought through this patent application. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view schematically showing one example of the configuration of a pressure-sensitive adhesive sheet. [Figure 2] FIG. 10 is a cross-sectional view schematically showing another example of the configuration of the pressure-sensitive adhesive sheet. DETAILED DESCRIPTION OF THE INVENTION

[0016] Preferred embodiments of the present invention are described below. Matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings for carrying out the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. Furthermore, in the following drawings, components and parts that perform the same function may be denoted by the same reference numerals, and redundant explanations may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic for the purpose of clearly explaining the present invention, and do not necessarily accurately represent the size or scale of the actual product provided.

[0017] <Adhesive composition> The pressure-sensitive adhesive composition disclosed herein is a hot-melt pressure-sensitive adhesive composition. Herein, the term "hot-melt pressure-sensitive adhesive composition" refers to a pressure-sensitive adhesive composition used in a hot-melt (heat-fused) form when forming a pressure-sensitive adhesive layer. A hot-melt pressure-sensitive adhesive composition is typically a solvent-free pressure-sensitive adhesive composition that is substantially free of solvent. In this specification, a pressure-sensitive adhesive composition being "solvent-free" or "substantially free of solvent" means that the solvent content in the entire pressure-sensitive adhesive composition is 1 wt % or less, more preferably 0.1 wt % or less, and even more preferably 0.01 wt % or less, and includes a case where the solvent content is 0 wt %. In this specification, a hot-melt pressure-sensitive adhesive composition may be simply referred to as a "pressure-sensitive adhesive composition."

[0018] (base polymer) The PSA composition disclosed herein contains a base polymer. The type of base polymer is not particularly limited. The PSA composition disclosed herein may be a PSA composition containing, as a base polymer (i.e., a component accounting for 50% by weight or more of the polymer components), one or more polymers that exhibit rubber elasticity at room temperature, such as acrylic polymers, rubber polymers (natural rubber, synthetic rubber, a mixture thereof, etc.), polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine-containing polymers. Here, when the PSA composition contains two or more polymers as base polymers, it includes the PSA composition containing a blend of the polymers, which is considered to be a single base polymer.

[0019] The PSA composition disclosed herein can be preferably implemented in an embodiment in which more than 50 wt % of the monomer components are (meth)acrylic monomers. The PSA composition disclosed herein is preferably a PSA composition containing, as a base polymer, an acrylic polymer that is a polymer of the monomer components, i.e., an acrylic PSA composition. In some preferred embodiments of the PSA composition, more than 70 wt %, more than 80 wt %, or more than 90 wt % of the polymer components contained in the composition may be acrylic polymers. 95 wt % or more or 98 wt % or more of the polymer components may be acrylic polymers.

[0020] In this specification, the term "acrylic polymer" refers to a polymer containing monomer units derived from (meth)acrylic monomers in the polymer structure, typically a polymer containing more than 50% by weight of monomer units derived from (meth)acrylic monomers. In this specification, the term "(meth)acrylic monomer" refers to a monomer having at least one (meth)acryloyl group per molecule. Here, the term "(meth)acryloyl group" refers to both acryloyl and methacryloyl groups. Therefore, the term "(meth)acrylic monomer" as used herein encompasses both monomers having an acryloyl group (acrylic monomers) and monomers having a methacryloyl group (methacrylic monomers). Similarly, in this specification, the term "(meth)acrylic acid" refers to both acrylic acid and methacrylic acid, and the term "(meth)acrylate" refers to both acrylate and methacrylate.

[0021] In a preferred embodiment of the technology disclosed herein, the PSA composition contains, as a base polymer, an acrylic polymer that is a polymer of monomer components whose main component is a (meth)acrylic monomer. In this specification, the term "main component" refers to a component that is contained in an amount of more than 50% by weight. The content of the "main component" in the monomer components is preferably 85% by weight or more, more preferably 90% by weight or more, even more preferably 92% by weight or more, and particularly preferably 95% by weight or more.

[0022] The pressure-sensitive adhesive composition disclosed herein is characterized by comprising at least two or more acrylic polymers as base polymers. The use of a base polymer having such a configuration makes it easier to achieve a good balance of multiple properties, such as improved adhesive properties and reduced viscosity in a molten state. In the technology disclosed herein, the base polymer comprises at least an acrylic polymer A and an acrylic polymer B. Here, the acrylic polymer A is a polymer of monomer components whose main component is a (meth)acrylic monomer A. The acrylic polymer B is a polymer of monomer components whose main component is a (meth)acrylic monomer B. The use of a base polymer having such a configuration makes it easier to achieve both good adhesive properties (e.g., adhesive strength and holding power) and reduced viscosity when heated and melted.

[0023] (Acrylic polymer A) In the technology disclosed herein, the base polymer contains an acrylic polymer A, which is a polymer of a monomer component whose main component is a (meth)acrylic monomer A having an alkyl group with 4 to 8 carbon atoms. In a preferred embodiment of the technology disclosed herein, the (meth)acrylic monomer A is an alkyl(meth)acrylate having an alkyl group with 4 to 8 carbon atoms at the ester terminal. Hereinafter, an alkyl(meth)acrylate having an alkyl group with X to Y carbon atoms at the ester terminal will be referred to as "C X-Y It is sometimes written as "alkyl (meth)acrylate." (Meth)acrylic monomer A is C 4-8 In the case of alkyl (meth)acrylate, C 4-8 C in alkyl (meth)acrylate 4-8 The structure of the alkyl group is not particularly limited, and both straight-chain and branched-chain alkyl groups can be used. 4-8 The alkyl (meth)acrylates may be used alone or in combination of two or more. 4-8Examples include acrylic polymers containing at least one type of alkyl (meth)acrylate as a monomer unit.

[0024] C with a linear alkyl group at the ester end 4-8 Examples of alkyl (meth)acrylates include n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, and n-octyl (meth)acrylate. Also, C 16 alkyl acrylates having a branched alkyl group at the ester end are also known. 4-8 Examples of alkyl (meth)acrylates include t-butyl (meth)acrylate, isobutyl (meth)acrylate, isopentyl (meth)acrylate, t-pentyl (meth)acrylate, neopentyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isooctyl (meth)acrylate. The technology disclosed herein relates to a method for producing a (meth)acrylic monomer A containing C 4-8 It is preferable to use one or more alkyl acrylates selected from the group consisting of C, ... 4-8 Suitable examples of alkyl acrylates include n-butyl acrylate, 2-ethylhexyl acrylate, and isooctyl acrylate, with n-butyl acrylate and 2-ethylhexyl acrylate being particularly preferred.

[0025] The content of the (meth)acrylic monomer A in the monomer components constituting the acrylic polymer A is, for example, more than 50% by weight, preferably 85% by weight or more, more preferably 90% by weight or more, even more preferably 92% by weight or more, and particularly preferably 95% by weight or more.

[0026] The monomer units constituting the acrylic polymer A may contain, in addition to the (meth)acrylic monomer A as the main component, other secondary monomers (copolymerizable monomers) copolymerizable with the (meth)acrylic monomer A, as necessary. As the secondary monomer copolymerizable with the (meth)acrylic monomer A, monomers having a functional group (e.g., a carboxy group, a hydroxyl group, an amide group, etc.) can be suitably used. The functional group-containing monomer can be useful for introducing crosslinking points into the acrylic polymer A and for increasing the cohesive strength of the acrylic polymer A and, ultimately, the base polymer.

[0027] As the secondary monomer, for example, the following functional group-containing monomers can be used alone or in combination of two or more. Hydroxyl group-containing monomers: for example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol; and ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether. Carboxy group-containing monomers: for example, ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), crotonic acid, isocrotonic acid, etc.; ethylenically unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, etc. Acid anhydride group-containing monomers: for example, maleic anhydride, itaconic anhydride. Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, methyl-N-vinylpyrrolidone, vinylpyridine, vinylpyrazine, vinylpyrimidine, N-vinylpiperidone, N-vinylpiperazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, N-(meth)acryloylmorpholine, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, and the like. Amide group-containing monomers: for example, (meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(t-butyl)(meth)acrylamide; N-alkyl(meth)acrylamides such as N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, and Nn-butyl(meth)acrylamide; N-vinylcarboxylic acid amides such as N-vinylacetamide; monomers having a hydroxyl group and an amide group, for example, N-(2-hydroxyethyl)(meth)acrylamide, N- N-hydroxyalkyl(meth)acrylamides such as (2-hydroxypropyl)(meth)acrylamide, N-(1-hydroxypropyl)(meth)acrylamide, N-(3-hydroxypropyl)(meth)acrylamide, N-(2-hydroxybutyl)(meth)acrylamide, N-(3-hydroxybutyl)(meth)acrylamide, and N-(4-hydroxybutyl)(meth)acrylamide; monomers having an alkoxy group and an amide group, for example, N-alkoxyalkyl(meth)acrylamides such as N-methoxymethyl(meth)acrylamide, N-methoxyethyl(meth)acrylamide, and N-butoxymethyl(meth)acrylamide; and N,N-dialkylaminoalkyl(meth)acrylamides such as N,N-dimethylaminopropyl(meth)acrylamide. Amino group-containing monomers: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate. Monomers having a succinimide skeleton: for example, N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, N-(meth)acryloyl-8-oxyhexamethylene succinimide, and the like. Maleimides: for example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, etc. Itaconimides: for example, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, and the like. Epoxy group-containing monomers: for example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, allyl glycidyl ether. Cyano group-containing monomers: for example, acrylonitrile, methacrylonitrile. Keto group-containing monomers: for example, diacetone (meth)acrylamide, diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate. Alkoxysilyl group-containing monomers: for example, alkoxysilyl group-containing (meth)acrylates such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane; and alkoxysilyl group-containing vinyl compounds such as vinyltrimethoxysilane and vinyltriethoxysilane. Amino group-containing monomers: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate. Monomers having an epoxy group: for example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, allyl glycidyl ether. Monomers containing a sulfonic acid group or a phosphoric acid group: for example, styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, 2-hydroxyethyl acryloylphosphate, etc. Isocyanate group-containing monomers: for example, 2-isocyanatoethyl (meth)acrylate, (meth)acryloyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate.

[0028] When using such a functional group-containing monomer, the amount used is not particularly limited, but is usually 0.01 wt% or more of the total amount of monomer components constituting the acrylic polymer A. To maximize the effect of using the functional group-containing monomer, the amount of functional group-containing monomer used may be 0.1 wt% or more, or even 1 wt% or more of the total amount of monomer components. Furthermore, the amount of functional group-containing monomer used may be 50 wt% or less of the total amount of monomer components, preferably 15 wt% or less, more preferably 10 wt% or less, even more preferably 8 wt% or less, and particularly preferably 5 wt% or less. This prevents the cohesive strength of the PSA from becoming too high, thereby improving adhesion to the adherend.

[0029] The pressure-sensitive adhesive composition disclosed herein can be preferably implemented in an embodiment in which the monomer components constituting the acrylic polymer A include a (meth)acrylic monomer A and further include one or both of acrylic acid and a hydroxyl group-containing monomer. As the hydroxyl group-containing monomer, a hydroxyalkyl (meth)acrylate can be preferably used. Hydroxy C such as 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA) can be preferably used. 1-4 Alkyl acrylates are particularly preferred.

[0030] The starting monomer material used in preparing the acrylic polymer A may contain a sub-monomer other than the functional group-containing monomer described above, for the purpose of increasing the cohesive strength of the acrylic polymer A or the like. Non-limiting specific examples of the secondary monomer include the following: Alkoxy group-containing monomers: for example, alkoxyalkyl (meth)acrylates (alkoxyalkyl (meth)acrylates) such as 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, and 2-ethoxyethyl (meth)acrylate; alkoxy(poly)alkylene glycol (meth)acrylates such as methoxyethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate. Vinyl esters: for example, vinyl acetate, vinyl propionate, etc. Vinyl ethers: for example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether. Aromatic vinyl compounds: for example, styrene, α-methylstyrene, vinyltoluene, etc. Olefins: for example, ethylene, butadiene, isoprene, isobutylene, etc. (Meth)acrylic acid esters having an alicyclic hydrocarbon group: for example, (meth)acrylates containing an alicyclic hydrocarbon group such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and adamantyl (meth)acrylate. Aromatic ring-containing (meth)acrylates: for example, aryl (meth)acrylates such as phenyl (meth)acrylate, aryloxyalkyl (meth)acrylates such as phenoxyethyl (meth)acrylate, and arylalkyl (meth)acrylates such as benzyl (meth)acrylate. Other examples include heterocyclic ring-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen atom-containing monomers such as vinyl chloride and fluorine atom-containing (meth)acrylates, organosiloxane chain-containing monomers such as silicone (meth)acrylates, and (meth)acrylic acid esters obtained from terpene compound derivative alcohols. Such other secondary monomers may be used alone or in combination of two or more. The amount of such other secondary monomers is not particularly limited and may be appropriately selected depending on the purpose and application, but is preferably 20% by weight or less (e.g., 2 to 20% by weight, typically 3 to 10% by weight) of the total monomer raw materials for the acrylic polymer A.

[0031] In a preferred embodiment of the technology disclosed herein, the base polymer of the pressure-sensitive adhesive composition contains one or more acrylic polymers selected from acrylic polymer A. From the viewpoint of adjusting the adhesive properties, the base polymer preferably contains two or more acrylic polymers selected from acrylic polymer A. Furthermore, from the viewpoint of simplifying the composition, the base polymer preferably contains one acrylic polymer selected from acrylic polymer A.

[0032] (Acrylic polymer B) In the technology disclosed herein, the base polymer contains, in addition to the acrylic polymer A, an acrylic polymer B which is a polymer of monomer components containing a (meth)acrylic monomer B as a main component, as described below.

[0033] The (meth)acrylic monomer B is a (meth)acrylic monomer having an alkyl group having 9 to 12 carbon atoms. In a preferred embodiment of the technology disclosed herein, the (meth)acrylic monomer B is an alkyl (meth)acrylate having an alkyl group having 9 to 12 carbon atoms at the ester terminal. The (meth)acrylic monomer B is C 9-12 In the case of alkyl (meth)acrylate, C 9-12 C in alkyl (meth)acrylate 9-12 The structure of the alkyl group is not particularly limited, and both straight-chain and branched-chain alkyl groups can be used. 9-12 The alkyl (meth)acrylates can be used alone or in combination of two or more.

[0034] C with a linear alkyl group at the ester end 9-12 Examples of alkyl (meth)acrylates include n-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-undecyl (meth)acrylate, and n-dodecyl (meth)acrylate (or lauryl (meth)acrylate). Also, C alkyl (meth)acrylates having a branched alkyl group at the ester end are also known. 9-12 Examples of alkyl (meth)acrylates include isononyl (meth)acrylate, isodecyl (meth)acrylate, 2-propylheptyl (meth)acrylate, isoundecyl (meth)acrylate, and isododecyl (meth)acrylate. 9-12 It is preferable to use one or more alkyl acrylates selected from the group consisting of C, ... 9-12 Suitable examples of alkyl acrylates include isononyl acrylate, isodecyl acrylate, and n-dodecyl (meth)acrylate (or lauryl acrylate).

[0035] The content of (meth)acrylic monomer B in the monomer components constituting the acrylic polymer B is, for example, more than 50% by weight, preferably 85% by weight or more, more preferably 90% by weight or more, even more preferably 92% by weight or more, and particularly preferably 95% by weight or more.

[0036] The monomer units constituting the acrylic polymer B may contain, in addition to the (meth)acrylic monomer B as the main component, other secondary monomers (copolymerizable monomers) copolymerizable with the (meth)acrylic monomer B, as necessary. As the secondary monomer copolymerizable with the (meth)acrylic monomer B, a monomer having a functional group (e.g., a carboxy group, a hydroxyl group, an amide group, etc.) can be suitably used. The functional group-containing monomer can be useful for introducing crosslinking points into the acrylic polymer B and for increasing the cohesive strength of the acrylic polymer B and, ultimately, the base polymer.

[0037] The above-mentioned secondary monomer can be the same as the other secondary monomer copolymerizable with the (meth)acrylic monomer A. Specific examples of secondary monomers that can be used as raw materials for the acrylic polymer B include the same secondary monomers that can be used as raw materials for the acrylic polymer A.

[0038] When using such a functional group-containing monomer, the amount used is not particularly limited, but is usually 0.01 wt% or more of the total amount of monomer components constituting the acrylic polymer B. To maximize the effect of using the functional group-containing monomer, the amount of functional group-containing monomer used may be 0.1 wt% or more, or even 1 wt% or more of the total amount of monomer components. Furthermore, the amount of functional group-containing monomer used may be 50 wt% or less of the total amount of monomer components, preferably 15 wt% or less, more preferably 10 wt% or less, even more preferably 8 wt% or less, and particularly preferably 5 wt% or less. This prevents the cohesive strength of the PSA from becoming too high, thereby improving adhesion to the adherend.

[0039] The pressure-sensitive adhesive composition disclosed herein can be preferably implemented in an embodiment in which the monomer components constituting the acrylic polymer B include a (meth)acrylic monomer B and further include one or both of acrylic acid and a hydroxyl group-containing monomer. As the hydroxyl group-containing monomer, a hydroxyalkyl (meth)acrylate can be preferably used. Hydroxy C such as 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA) can be preferably used. 1-4 Alkyl acrylates are particularly preferred.

[0040] The starting monomer material used in preparing the acrylic polymer B may contain a secondary monomer other than the functional group-containing monomer described above, for the purpose of increasing the cohesive strength of the acrylic polymer B, etc. Such secondary monomers may be the same as the secondary monomers used in preparing the acrylic polymer A described above. Such secondary monomers may be used alone or in combination of two or more. The amount of such secondary monomers may be appropriately selected depending on the purpose and application, and is not particularly limited. However, for example, it is preferable that the amount of such secondary monomers be 20% by weight or less (e.g., 2 to 20% by weight, typically 3 to 10% by weight) of the total starting monomer material for the acrylic polymer B.

[0041] In a preferred embodiment of the technology disclosed herein, the base polymer of the pressure-sensitive adhesive composition contains one or more polymers selected from acrylic polymer B. From the viewpoint of adjusting the adhesive properties and viscosity in a molten state, the base polymer preferably contains two or more acrylic polymers selected from acrylic polymer B. Furthermore, from the viewpoint of simplifying the composition, the base polymer preferably contains one acrylic polymer selected from acrylic polymer B.

[0042] In a preferred embodiment of the technology disclosed herein, the base polymer contained in the PSA composition is a mixture of acrylic polymer A and acrylic polymer B. In other words, in the technology disclosed herein, the base polymer of the PSA composition can be a mixture obtained by blending one or more acrylic polymers selected from acrylic polymer A with one or more acrylic polymers selected from acrylic polymer B. From the viewpoint of simplifying the composition, in one embodiment of the technology disclosed herein, the base polymer may be a mixture of two or more acrylic polymers selected from acrylic polymer A and one acrylic polymer selected from acrylic polymer B, a mixture of one acrylic polymer selected from acrylic polymer A and two or more acrylic polymers selected from acrylic polymer B, or a mixture of one acrylic polymer selected from acrylic polymer A and one acrylic polymer selected from acrylic polymer B. Here, the type of acrylic polymer can be distinguished by the type, ratio, arrangement, etc. of monomer units constituting the acrylic polymer, the weight-average molecular weight of the polymer, etc.

[0043] In the technology disclosed herein, the content of acrylic polymer B is preferably 10% by weight or more when the total amount of acrylic polymer A and acrylic polymer B in the base polymer is taken as 100% by weight. The content of acrylic polymer B is more preferably 20% by weight or more, and even more preferably 30% by weight or more. In a preferred embodiment, the content of acrylic polymer B may be 40% by weight or more, 45% by weight or more, or 50% by weight or more. The viscosity of the pressure-sensitive adhesive composition in a heat-molten state tends to decrease more favorably as the content of acrylic polymer B increases relative to the content of acrylic polymer A.

[0044] Furthermore, in the technology disclosed herein, when the total amount of acrylic polymer A and acrylic polymer B in the base polymer is taken as 100% by weight, the content of acrylic polymer B is preferably 90% by weight or less, more preferably 80% by weight or less, and even more preferably 70% by weight or less. In a preferred embodiment, the content of acrylic polymer B may be 60% by weight or less, 55% by weight or less, or 50% by weight or less. The higher the content of acrylic polymer A compared to the content of acrylic polymer B, the more the adhesive properties (e.g., adhesive strength or holding power) tend to improve.

[0045] When the base polymer contains two or more types of acrylic polymer A, the content of the acrylic polymer A refers to the total amount of each acrylic polymer A. Similarly, when the base polymer contains two or more types of acrylic polymer B, the content of the acrylic polymer B refers to the total amount of each acrylic polymer B.

[0046] (Other acrylic polymers) In the technology disclosed herein, the PSA composition may contain, as a base polymer, an acrylic polymer other than the acrylic polymer A and the acrylic polymer B. Examples of the other acrylic polymer include C 2-3 Alkyl (meth)acrylate and C 13-18 Examples include polymers of monomer components whose main component is alkyl (meth)acrylate. 2-3 Examples of alkyl (meth)acrylates include ethyl (meth)acrylate, n-propyl (meth)acrylate, and isopropyl (meth)acrylate. 13-18Examples of alkyl (meth)acrylates include n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, n-pentadecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-heptadecyl (meth)acrylate, n-octadecyl (meth)acrylate, isotridecyl (meth)acrylate, isomistyryl (meth)acrylate, isopentadecyl (meth)acrylate, isohexadecyl (meth)acrylate, isoheptadecyl (meth)acrylate, isostearyl (meth)acrylate, etc. The technology disclosed herein can be suitably implemented in an embodiment in which the base polymer is substantially free of other acrylic polymers than acrylic polymer A and acrylic polymer B.

[0047] The method for polymerizing the monomer raw materials is not particularly limited, and various polymerization methods known as methods for synthesizing acrylic polymers, such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization, can be appropriately employed. For example, solution polymerization is preferably employed. The monomer supply method for solution polymerization can be appropriately selected from a conventionally known organic solvent. For example, any one solvent or a mixture of two or more solvents selected from aromatic compounds (typically aromatic hydrocarbons) such as toluene; esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols (e.g., monohydric alcohols having 1 to 4 carbon atoms) such as isopropyl alcohol; ethers such as tert-butyl methyl ether; and ketones such as methyl ethyl ketone can be used. The polymerization temperature can be appropriately selected depending on the types of monomer and solvent used, the type of polymerization initiator, etc., and can be, for example, about 20°C to 120°C (typically 40°C to 80°C). Solution polymerization produces a polymerization reaction liquid in which a polymer of the monomer raw material is dissolved in the polymerization solvent. The pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer can be preferably produced using the polymerization reaction liquid.

[0048] For polymerization, known or conventional thermal polymerization initiators or photopolymerization initiators can be used depending on the polymerization method, polymerization mode, etc. Examples of thermal polymerization initiators that can be used include azo-based polymerization initiators, peroxide-based initiators, redox-based initiators formed by combining peroxides with reducing agents, and substituted ethane-based initiators. Examples of photopolymerization initiators include α-ketol-based photoinitiators, acetophenone-based photoinitiators, benzoin ether-based photoinitiators, ketal-based photoinitiators, aromatic sulfonyl chloride-based photoinitiators, photoactive oxime-based photoinitiators, benzophenone-based photoinitiators, thioxanthone-based photoinitiators, and acylphosphinoxide-based photoinitiators. The polymerization initiators can be used alone or in appropriate combinations of two or more.

[0049] The amount of the polymerization initiator used may be any amount that is normally used, and can be selected, for example, from the range of about 0.005 to 1 part by weight (typically 0.01 to 1 part by weight) per 100 parts by weight of the total monomer raw materials.

[0050] The PSA composition disclosed herein may further contain a polymer other than an acrylic polymer as a secondary polymer, if necessary. Suitable examples of the secondary polymer include those other than acrylic polymers among the various polymers exemplified as polymers that can be contained in the PSA layer. When the PSA composition disclosed herein contains a secondary polymer in addition to an acrylic polymer, the content of the secondary polymer is suitably less than 100 parts by weight per 100 parts by weight of the acrylic polymer, preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and even more preferably 10 parts by weight or less. The content of the secondary polymer may be 5 parts by weight or less, or even 1 part by weight or less, per 100 parts by weight of the acrylic polymer. The technology disclosed herein can be preferably implemented, for example, in an embodiment in which 99.5 to 100% by weight of the polymer contained in the PSA composition is an acrylic polymer.

[0051] The molecular weight of the acrylic polymer A is not particularly limited and can be set within an appropriate range depending on the required performance. The weight average molecular weight (Mw) of the acrylic polymer A is approximately 5 × 10 4 It is appropriate that the density is equal to or greater than 75×10 4 More preferably, approximately 80×10 4 More preferably, approximately 85×10 4 or more (for example, approximately 90 x 10 4 The technology disclosed herein realizes a pressure-sensitive adhesive composition that exhibits suitably low viscosity even when heated and melted, and therefore, even when an acrylic polymer A having an Mw equal to or greater than the above-mentioned predetermined value is used as the base polymer, a pressure-sensitive adhesive composition that can easily form a pressure-sensitive adhesive layer is easily realized. The upper limit of the Mw of the acrylic polymer A is not particularly limited, and is approximately 150 × 10 4It is appropriate that the value is equal to or less than 120×10 4 or less, more preferably approximately 115×10 4 Below (for example, approximately 110 x 10 4 When the Mw of the acrylic polymer A is within the above range, the elastic modulus of the pressure-sensitive adhesive can be easily adjusted to a preferred range, and the pressure-sensitive adhesive can easily exhibit good cohesive strength.

[0052] The molecular weight of the acrylic polymer B is not particularly limited and can be set within an appropriate range depending on the required performance. The weight average molecular weight (Mw) of the acrylic polymer B is approximately 5 × 10 4 It is appropriate that the density is equal to or greater than 75×10 4 More preferably, approximately 80×10 4 More preferably, approximately 85×10 4 or more (for example, approximately 90 x 10 4 The technology disclosed herein realizes a pressure-sensitive adhesive composition that exhibits suitably low viscosity even when heated and melted, and therefore, even when an acrylic polymer B having an Mw equal to or greater than the above-mentioned predetermined value is used as the base polymer, a pressure-sensitive adhesive composition that can easily form a pressure-sensitive adhesive layer is easily realized. The upper limit of the Mw of the acrylic polymer B is not particularly limited, and is approximately 150×10 4 It is appropriate that the value is equal to or less than 120×10 4 or less, more preferably approximately 115×10 4 Below (for example, approximately 110 x 10 4 When the Mw of the acrylic polymer B is within the above range, the elastic modulus of the pressure-sensitive adhesive can be easily adjusted to a preferred range, and the pressure-sensitive adhesive can easily exhibit good cohesive strength.

[0053] Here, the Mw of the base polymer (typically acrylic polymer A and acrylic polymer B) refers to a polystyrene-equivalent value determined based on gel permeation chromatography (GPC) measurement. A GPC measurement device that can be used is, for example, a Tosoh HLC-8220. Specifically, the Mw of the base polymer can be measured by the method described in the Examples below.

[0054] (glass transition temperature (Tg)) The acrylic polymer A contained in the pressure-sensitive adhesive composition disclosed herein can be set, for example, so that its glass transition temperature (Tg), calculated based on the composition of the monomer components constituting the acrylic polymer A, is less than 0°C. The acrylic polymer B contained in the pressure-sensitive adhesive composition disclosed herein can be set, for example, so that its glass transition temperature (Tg), calculated based on the composition of the monomer components constituting the acrylic polymer B, is less than 0°C. Here, the Tg calculated based on the composition of the monomer components refers to the Tg calculated by the Fox equation based on the composition of the monomer components. The Fox equation, as shown below, is a relational expression between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer. 1 / Tg=Σ(Wi / Tgi) In the above Fox formula, Tg represents the glass transition temperature (unit: K) of the copolymer, Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio by weight), and Tgi represents the glass transition temperature (unit: K) of the homopolymer of monomer i.

[0055] The glass transition temperature of a homopolymer used to calculate Tg is a value listed in a publicly available document. Specifically, values ​​are listed in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989). For monomers for which multiple values ​​are listed in the Polymer Handbook, the highest value is used. For the glass transition temperature of a homopolymer of a monomer not listed in the Polymer Handbook, the value obtained by the measurement method described in JP-A-2007-51271 can be used.

[0056] The Tg calculated based on the composition of the monomer components can be understood as the Tg of a polymer of the monomer components. The Tg of the acrylic polymer A calculated in this manner is preferably −10° C. or lower, and may be −20° C. or lower, −30° C. or lower, or −40° C. or lower. A lower Tg tends to improve adhesion to an adherend. In some embodiments, the Tg of the acrylic polymer A may be −50° C. or lower, −55° C. or lower, or −60° C. or lower. There is no particular lower limit for the Tg of the acrylic polymer A, but from the viewpoints of material availability and improved cohesion of the pressure-sensitive adhesive layer, it is usually appropriate that the Tg be −80° C. or higher, and preferably −70° C. or higher.

[0057] The Tg of the acrylic polymer B is preferably 150°C or lower, and may be 50°C or lower, 30°C or lower, or 10°C or lower. A lower Tg tends to improve adhesion to an adherend. In some embodiments, the Tg of the acrylic polymer B may be -20°C or lower, -35°C or lower, or -50°C or lower. There is no particular lower limit for the Tg of the acrylic polymer B, but from the viewpoint of easy availability of materials and improving the cohesiveness of the pressure-sensitive adhesive layer, it is usually appropriate that the Tg is -80°C or higher, and preferably -70°C or higher. In some embodiments, the Tg of the acrylic polymer B may be -20°C or higher, -10°C or higher, or 0°C or higher.

[0058] (viscosity) In the technology disclosed herein, the viscosity of the pressure-sensitive adhesive composition is not particularly limited. The shear viscosity of the pressure-sensitive adhesive composition at 130°C is preferably 7000 Pa·s or less, more preferably 6800 Pa·s or less, and even more preferably 6700 Pa·s or less. From the viewpoint of ease of extrusion molding of the pressure-sensitive adhesive layer, the shear viscosity of the pressure-sensitive adhesive composition at 130°C is usually appropriate to be 500 Pa·s or more, and preferably 1000 Pa·s or more (e.g., 1500 Pa·s or more). The shear viscosity of the pressure-sensitive adhesive composition at 130°C can be measured by the method described in the Examples below.

[0059] When measuring the shear viscosity of a pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition used for measurement preferably does not contain a crosslinker. Hereinafter, a pressure-sensitive adhesive composition that does not contain a crosslinker is also referred to as a pressure-sensitive adhesive composition PL. When the shear viscosity of the pressure-sensitive adhesive composition PL at 130°C is within the above-mentioned range, the pressure-sensitive adhesive composition PL or a pressure-sensitive adhesive composition obtained by adding a crosslinker to the pressure-sensitive adhesive composition PL can be used in extrusion molding to suitably mold a pressure-sensitive adhesive layer.

[0060] The pressure-sensitive adhesive composition disclosed herein may contain a tackifier. The tackifier is not particularly limited, but examples thereof include rosin-based tackifiers, terpene-based tackifiers, phenol-based tackifiers, hydrocarbon-based tackifiers, ketone-based tackifiers, polyamide-based tackifiers, epoxy-based tackifiers, and elastomer-based tackifiers. One tackifier may be used alone, or two or more tackifiers may be used in combination.

[0061] Examples of rosin-based tackifiers include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin, modified rosins obtained by modifying these unmodified rosins through polymerization, disproportionation, hydrogenation, etc. (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, and other chemically modified rosins), and various rosin derivatives. Examples of the rosin derivative include rosin phenolic resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, etc.) using an acid catalyst and then thermally polymerizing the resulting mixture; Rosin ester resins such as rosin ester compounds (unmodified rosin esters) obtained by esterifying unmodified rosin with alcohols, and modified rosin ester compounds (polymerized rosin esters, stabilized rosin esters, disproportionated rosin esters, fully hydrogenated rosin esters, partially hydrogenated rosin esters, etc.) obtained by esterifying modified rosins such as polymerized rosin, stabilized rosin esters, disproportionated rosin esters, fully hydrogenated rosin esters, partially hydrogenated rosin esters, etc.) with alcohols; Unsaturated fatty acid modified rosin resins, which are unmodified rosin or modified rosin (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, etc.) modified with unsaturated fatty acids; unsaturated fatty acid modified rosin ester resin obtained by modifying a rosin ester resin with an unsaturated fatty acid; Unmodified rosin, modified rosin (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, etc.), unsaturated fatty acid modified rosin resin, or unsaturated fatty acid modified rosin ester resin, rosin alcohol resin in which the carboxyl group has been reduced; Metal salts of rosin-based resins (particularly rosin ester-based resins) such as unmodified rosin, modified rosin, and various rosin derivatives are included.

[0062] Examples of terpene-based tackifiers include terpene-based resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers, as well as modified terpene-based resins obtained by modifying these terpene-based resins (such as phenol-modified, aromatic-modified, hydrogenated, and hydrocarbon-modified) (e.g., terpene-phenolic resins, styrene-modified terpene resins, aromatic-modified terpene resins, and hydrogenated terpene resins).

[0063] Examples of phenolic tackifiers include condensates of various phenols (e.g., phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcinol, etc.) with formaldehyde (e.g., alkylphenol resins, xylene formaldehyde resins, etc.), resols obtained by addition reaction of the above-mentioned phenols with formaldehyde using an alkali catalyst, and novolaks obtained by condensation reaction of the above-mentioned phenols with formaldehyde using an acid catalyst.

[0064] Examples of hydrocarbon-based tackifiers include various hydrocarbon resins such as aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone-indene resins.

[0065] (Crosslinking agent) In a preferred embodiment of the technology disclosed herein, the pressure-sensitive adhesive composition further contains a crosslinking agent. There are no particular limitations on the crosslinking agent, and various crosslinking agents can be used. In a preferred embodiment of the technology disclosed herein, examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, melamine-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, hydrazine-based crosslinking agents, and amine-based crosslinking agents. These crosslinking agents can be used alone or in combination of two or more.

[0066] As the isocyanate-based crosslinking agent, a bifunctional or polyfunctional isocyanate compound can be used. Examples include aromatic isocyanates such as tolylene diisocyanate, xylene diisocyanate, polymethylene polyphenyl diisocyanate, tris(p-isocyanatophenyl)thiophosphate, and diphenylmethane diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; and aliphatic isocyanates such as hexamethylene diisocyanate. Commercially available isocyanate adducts include trimethylolpropane / tolylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, product name "Coronate L"), trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, product name "Coronate HL"), and isocyanurate of hexamethylene diisocyanate (manufactured by Tosoh Corporation, product name "Coronate HX").

[0067] As the epoxy-based crosslinking agent, those having two or more epoxy groups per molecule can be used without particular limitation. Epoxy-based crosslinking agents having 3 to 5 epoxy groups per molecule are preferred. Specific examples of epoxy-based crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, etc. Commercially available epoxy-based crosslinking agents include "TETRAD-X" and "TETRAD-C" manufactured by Mitsubishi Gas Chemical Company, Inc., "Epicron CR-5L" manufactured by DIC Corporation, "Denacol EX-512," "Denacol EX-411," and "Denacol EX-321" manufactured by Nagase ChemteX Corporation, and "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd.

[0068] The amount of crosslinking agent used is not particularly limited and can be appropriately set so as to obtain the desired effect. From the viewpoint of adhesion to the adherend and bonding reliability, the amount of crosslinking agent used per 100 parts by weight of the base polymer is usually about 15 parts by weight or less, preferably about 12 parts by weight or less, more preferably about 10 parts by weight or less, and may be less than 7 parts by weight or less than 5 parts by weight. The lower limit of the amount of crosslinking agent used is not particularly limited. From the viewpoint of improving adhesive performance, the amount of crosslinking agent used per 100 parts by weight of the base polymer is usually 0.01 parts by weight or more, preferably 0.05 parts by weight or more, more preferably 0.1 parts by weight or more, even more preferably 0.2 parts by weight or more, and may be 0.5 parts by weight or more, 1 part by weight or more, or 1.5 parts by weight or more.

[0069] A crosslinking catalyst may be used to more effectively promote the reaction of any of the above crosslinking agents. Examples of crosslinking catalysts that can be used preferably include tin-based catalysts (especially dioctyltin dilaurate) and amine-based catalysts (e.g., 1-isobutyl-2-methylimidazole). The amount of the crosslinking catalyst used is not particularly limited, but can be, for example, approximately 0.0001 to 1 part by weight per 100 parts by weight of the base polymer.

[0070] (polyfunctional monomer) In preparing the PSA composition disclosed herein, a polyfunctional monomer may be used as needed. The polyfunctional monomer may be used in place of or in combination with the crosslinking agent described above, and may be useful for purposes such as adjusting cohesive strength. Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyldiol (meth)acrylate, and hexyldiol di(meth)acrylate. Among them, preferred polyfunctional monomers include trimethylolpropane tri(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. The polyfunctional monomers can be used singly or in combination of two or more. The amount of polyfunctional monomer used varies depending on the molecular weight, number of functional groups, etc., but is usually suitably in the range of about 0.01 to 3.0 parts by weight per 100 parts by weight of the base polymer. The adhesive composition disclosed herein can be preferably implemented in an embodiment that is substantially free of polyfunctional monomers.

[0071] In addition, the pressure-sensitive adhesive composition in the technology disclosed herein may contain, as needed, known additives that can be used in pressure-sensitive adhesives, such as leveling agents, plasticizers, softeners, colorants (dyes, pigments, etc.), antistatic agents, antioxidants, UV absorbers, antioxidants, light stabilizers, and preservatives, as long as the effects of the present invention are not significantly impaired.

[0072] <Formation of adhesive layer> The PSA layer of the PSA sheet disclosed herein may be a PSA layer formed from a hot-melt PSA composition containing a base polymer (e.g., a mixture of acrylic polymer A and acrylic polymer B) and, if necessary, other optional components. The PSA composition disclosed herein can be molded in a heated, molten state, and then subjected to an aging step to form a PSA layer.

[0073] The method for forming the hot melt pressure-sensitive adhesive composition disclosed herein into a film (or sheet) is not particularly limited, and can be carried out by any known appropriate method. The pressure-sensitive adhesive composition disclosed herein can be formed by, for example, a calendar method, a casting method, an inflation extrusion method, a T-die extrusion method, or the like. For example, when the pressure-sensitive adhesive composition disclosed herein is formed into a film by melt extrusion, the pressure-sensitive adhesive composition is heated to a relatively high temperature (typically about 90 to 110°C, e.g., about 100°C) to be in a molten state with high fluidity. The molten pressure-sensitive adhesive composition is then extruded from a mold of an extrusion device to be formed into a film. The pressure-sensitive adhesive composition formed into a film is then aged by being left under a lower temperature condition (typically about 30 to 50°C, e.g., about 40°C) for a certain period of time or more (typically 12 hours or more, e.g., 24 hours or more), thereby forming a pressure-sensitive adhesive layer with suitable adhesive properties.

[0074] In the pressure-sensitive adhesive sheet disclosed herein, the thickness of the pressure-sensitive adhesive layer is not particularly limited and can be appropriately selected depending on the purpose. Usually, the thickness of the pressure-sensitive adhesive layer is about 5 to 1000 μm, and from the viewpoint of adhesion, etc., it is preferably about 10 μm or more (e.g., 15 μm or more, typically 25 μm or more), and preferably about 750 μm or less, more preferably 500 μm or less, and even more preferably about 400 μm or less (e.g., 300 μm or less, typically 200 μm or less).

[0075] <Adhesive sheet configuration example> The technology disclosed herein provides a pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer typically forms at least one surface of the pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet may be a substrate-attached pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one or both sides of a substrate (support), or may be a pressure-sensitive adhesive sheet not including a substrate (substrate-less pressure-sensitive adhesive sheet). The concept of PSA sheet here may include those called PSA tapes, PSA labels, PSA films, etc. The PSA sheet provided by the present specification may be in the form of a roll or a sheet. Alternatively, the PSA sheet may be in the form of a PSA sheet that has been further processed into various shapes.

[0076] Figures 1 and 2 are diagrams showing an example of the configuration of a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein. Pressure-sensitive adhesive sheet 1 shown in Figure 1 has a configuration in which one surface (first adhesive surface) 21A and the other surface (second adhesive surface) 21B of substrate-less pressure-sensitive adhesive layer 21 are protected by release liners 31 and 32, each of which has at least the pressure-sensitive adhesive layer side as a release surface. Pressure-sensitive adhesive sheet 2 shown in Figure 2 has a configuration in which one surface (first adhesive surface) 21A of pressure-sensitive adhesive layer 21 is protected by release liner 31, both of which have release surfaces. When rolled up, the other surface (second adhesive surface) 21B of pressure-sensitive adhesive layer 21 abuts against the back surface of release liner 31, so that the other surface 21B is also protected by release liner 31. A substrate-less or substrate-attached double-sided PSA sheet can be used as a substrate-attached single-sided PSA sheet by laminating a non-releasable substrate to one of the adhesive surfaces.

[0077] The PSA sheet before use (before application to an adherend) may be in the form of a release-liner PSA sheet in which the adhesive surface is protected with a release liner, as shown in Figures 1 and 2, for example. The release liner is not particularly limited, and examples that can be used include release liners in which the surface of a liner substrate such as a resin film or paper has been release-treated, and release liners made of low-adhesion materials such as fluorine-based polymers (polytetrafluoroethylene, etc.) and polyolefin-based resins (polyethylene, polypropylene, etc.). For example, silicone-based or long-chain alkyl-based release treating agents can be used for the release treatment. In some embodiments, a release-treated resin film can be preferably used as the release liner.

[0078] When the PSA sheet disclosed herein is in the form of a double-sided PSA sheet having a first adhesive surface and a second adhesive surface, the PSA constituting the first adhesive surface (first PSA) and the PSA constituting the second adhesive surface (second PSA) may have the same composition or different compositions. A substrate-less double-sided PSA sheet having different compositions on the first and second adhesive surfaces can be realized, for example, by a PSA layer having a multilayer structure in which two or more PSA layers with different compositions are laminated directly (without a substrate interposed therebetween).

[0079] <Base material> In single-sided or double-sided adhesive substrate-attached PSA sheets, the substrate supporting (backing) the PSA layer can be any of a variety of sheet-like substrates, such as resin film, paper, cloth, rubber sheet, foam sheet, metal foil, or a composite of these. The substrate may be a single layer or a laminate of substrates of the same or different types. In this specification, a single layer refers to a layer made of the same composition, and includes a configuration in which multiple layers made of the same composition are laminated.

[0080] In a preferred embodiment, a substrate (resin film substrate) mainly composed of a resin sheet can be used. Examples of resins constituting the substrate include polyolefin resins such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, very low-density polyethylene, random copolymer polypropylene, block copolymer polypropylene, homopolypropylene, polybutene, polymethylpentene, ethylene-vinyl acetate copolymer (EVA), ionomer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester (random, alternating) copolymer, ethylene-butene copolymer, and ethylene-hexene copolymer; polyurethane; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, and polybutylene terephthalate (PBT); polycarbonate; polyimide; polyether ether ketone; polyetherimide; polyamides such as aramid and wholly aromatic polyamide; polyphenyl sulfide; fluororesin; polyvinyl chloride; polyvinylidene chloride; cellulose resin; silicone resin; and the like. The above resins can be used alone or in combination of two or more to form the whole or part of the substrate (for example, any layer in a substrate having a laminated structure of two or more layers).

[0081] The base material may contain various additives, such as fillers (inorganic fillers, organic fillers, etc.), antioxidants, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, and colorants (pigments, dyes, etc.), as needed.

[0082] The substrate can be produced by any suitable method, such as a calendar method, a casting method, an inflation extrusion method, a T-die extrusion method, etc. If necessary, the substrate may be produced by a stretching treatment.

[0083] The surface of the substrate facing the pressure-sensitive adhesive layer may be subjected to known or conventional surface treatments, such as physical treatments such as corona discharge treatment, plasma treatment, sand matting treatment, ozone exposure treatment, flame exposure treatment, high-voltage shock exposure treatment, and ionizing radiation treatment; chemical treatments such as acid treatment, alkali treatment, and chromic acid treatment; and adhesion-enhancing treatments using coating agents (primers), for the purpose of imparting antistatic properties, etc. Furthermore, a conductive vapor-deposited layer containing a metal, an alloy, or an oxide thereof may be provided on the surface of the substrate.

[0084] In some preferred embodiments, an undercoat layer is provided on the surface of the substrate facing the pressure-sensitive adhesive layer. In other words, the undercoat layer can be disposed between the substrate and the pressure-sensitive adhesive layer. The material for forming the undercoat layer is not particularly limited, and one or more of urethane (polyisocyanate) resins, polyester resins, acrylic resins, polyamide resins, melamine resins, olefin resins, polystyrene resins, epoxy resins, phenolic resins, isocyanurate resins, polyvinyl acetate resins, etc. can be used. When an acrylic or other pressure-sensitive adhesive layer is provided on a resin film substrate via an undercoat layer, a polyester, urethane, or acrylic undercoat layer is preferred. When an acrylic pressure-sensitive adhesive layer is provided on a polyester substrate such as a PET film via an undercoat layer, a polyester undercoat layer is particularly preferred. The thickness of the undercoat layer is not particularly limited, and can usually be in the range of approximately 0.1 μm to 10 μm (e.g., 0.1 μm to 3 μm, typically 0.1 μm to 1 μm). The undercoat layer can be formed using a known or conventional coater such as a gravure roll coater or a reverse roll coater.

[0085] When the PSA sheet disclosed herein is a single-sided PSA sheet in which a PSA layer is provided on one side of a substrate, the side of the substrate on which the PSA layer is not formed (back side) may be subjected to a release treatment with a release treatment agent (back side treatment agent). The back side treatment agent that can be used to form the back side treatment layer is not particularly limited, and silicone-based back side treatment agents, fluorine-based back side treatment agents, long-chain alkyl-based back side treatment agents, and other known or commonly used treatment agents can be used depending on the purpose and application.

[0086] The thickness of the substrate is not particularly limited and can be selected appropriately depending on the purpose, but can generally be approximately 2 μm to 800 μm. From the viewpoint of the processability and handleability of the pressure-sensitive adhesive sheet, the thickness of the substrate is suitably 5 μm or more, preferably 10 μm or more or 20 μm or more, and may be 30 μm or more, or 40 μm or more. Furthermore, from the viewpoint of flexibility, the thickness of the substrate is usually suitably 300 μm or less, preferably 200 μm or less, may be 150 μm or less, 125 μm or less, 80 μm or less, or may be 60 μm or less.

[0087] The total thickness of the pressure-sensitive adhesive sheet disclosed herein (which may include a pressure-sensitive adhesive layer and a substrate, but does not include a release liner) is not particularly limited, and is suitably in the range of approximately 10 μm to 1200 μm. Taking into consideration adhesion and ease of handling, the total thickness of the pressure-sensitive adhesive sheet is preferably in the range of approximately 15 μm to 300 μm, and more preferably in the range of approximately 20 μm to 200 μm.

[0088] The adhesive strength of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited. For example, when a pressure-sensitive adhesive sheet cut to a size of 20 mm wide and 100 mm long is peeled from a stainless steel plate (SUS304BA plate) as an adherend at a peel angle of 180° and a tensile speed of 300 mm / min under an environment of 23°C and 50% RH, the peel strength is typically 1 N / 20 mm or more, preferably 4 N / 20 mm or more, more preferably 4.5 N / 20 mm or more, and particularly preferably 5 N / 20 mm or more. There are no particular limitations on the upper limit of the peel strength, but from the viewpoint of suppressing cohesive failure of the pressure-sensitive adhesive layer, it is preferably 10 N / 20 mm or less. The peel strength (adhesive strength) of the pressure-sensitive adhesive sheet can be specifically measured by the method described in the Examples below.

[0089] The holding power of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited. For example, a measurement sample is prepared by cutting a pressure-sensitive adhesive sheet to a size of 10 mm wide and 100 mm long and attaching it to a Bakelite plate (phenolic resin plate) as an adherend with an attachment length of 20 mm. In a holding power test, the measurement sample is placed in a vertical position with a load of 500 g applied to the free end of the measurement sample and left in an environment of 40°C for 60 minutes. In this test, it is preferable that the measurement sample does not fall off the Bakelite plate. The holding power of the pressure-sensitive adhesive sheet can be specifically measured by the method described in the Examples below. [Example]

[0090] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

[0091] (Preparation of Polymer A1) In a reaction vessel equipped with a Liebig condenser, a nitrogen inlet tube, a thermometer, a dropping funnel, and a stirrer, 100 parts of n-butyl acrylate (BA) and 5 parts of acrylic acid (AA) as raw monomer materials, 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and toluene as a polymerization solvent were added. After refluxing with nitrogen at room temperature for 1 hour, the mixture was heated and solution polymerized at 60°C for 5 hours and then at 80°C for 2 hours to prepare a solution of Polymer A1.

[0092] (Preparation of Polymer A2) A solution of polymer A2 was prepared in the same manner as in the preparation of polymer A1, except that 100 parts of 2-ethylhexyl acrylate (2EHA) was used instead of 100 parts of n-butyl acrylate (BA) as the monomer raw material.

[0093] (Preparation of Polymer B1) A solution of polymer B1 was prepared in the same manner as in the preparation of polymer A1, except that 100 parts of isononyl acrylate (INA) was used instead of 100 parts of n-butyl acrylate (BA) as a monomer raw material.

[0094] (Preparation of Polymer B2) A solution of polymer B2 was prepared in the same manner as in the preparation of polymer A1, except that 100 parts of lauryl acrylate (LA) was used instead of 100 parts of n-butyl acrylate (BA) as a monomer raw material.

[0095] The weight average molecular weights (Mw) of the polymers A1, A2, B1 and B2 prepared above were measured using the following apparatus under the following measurement conditions. Equipment: Tosoh HCL-8220 Separation column: Tosoh Corporation GMHHR-H(20) Detector: Differential refractive index detector Solvent: THF Flow rate: 0.5mL / min Measurement conditions: Column temperature 40°C

[0096] Table 1 shows the amounts of materials used in the preparation of polymer A1, polymer A2, polymer B1 and polymer B2, as well as the weight average molecular weight of each polymer measured by the above method.

[0097] [Table 1]

[0098] Example 1 (Preparation of Pressure-Sensitive Adhesive Composition) A pressure-sensitive adhesive composition PL was prepared by mixing the solution of polymer A2 and the solution of polymer B1 so that the solid content of polymer A2 was 90 parts and the solid content of polymer B1 was 10 parts. 2 parts of an isocyanate-based crosslinking agent (trimethylolpropane / tolylene diisocyanate trimer adduct, manufactured by Tosoh Corporation, trade name "Coronate L", solid content 75 wt%) was added as a crosslinking agent to the pressure-sensitive adhesive composition PL, and the toluene was then removed by drying under reduced pressure to obtain the hot-melt pressure-sensitive adhesive composition of Example 1.

[0099] <Examples 2 to 6, Comparative Examples 1 to 5> The hot melt pressure-sensitive adhesive compositions of each example were obtained in the same manner as in Example 1, except that the type and content of the polymer used were changed as shown in Tables 2 to 4.

[0100] [Adhesive strength measurement] The hot-melt pressure-sensitive adhesive composition prepared in each example was heated and melted at approximately 100°C using an extruder and extruded onto a 25 μm-thick PET substrate to produce a pressure-sensitive adhesive sheet with a 50 μm-thick pressure-sensitive adhesive layer laminated to the PET substrate. The pressure-sensitive adhesive sheet was cut to a size of 20 mm wide and 100 mm long to serve as a sample for measuring adhesive strength (peel strength). The adhesive surface of the measurement sample was pressed against a stainless steel plate (SUS304BA plate) using a 2 kg rubber roller in a single stroke at 23°C and 50% RH. After leaving the sample at 50°C for 2 hours, the peel strength (adhesion) [N / 20 mm] was measured at 23°C and 50% RH in accordance with JIS Z0237:2000 using a tensile tester at a peel angle of 180° and a tensile speed of 300 mm / min. The tensile tester used was a Shimadzu AG-IS triple tensile tester. The tensile tester may be the above-mentioned tester or an equivalent device. The measurement results are shown in the corresponding columns in Tables 2 to 4.

[0101] In addition, when the adhesive strength of the adhesive sheets produced using the hot melt adhesive compositions of Comparative Examples 3 and 5 was measured, the adhesive layers underwent cohesive failure.

[0102] [Measuring holding power] The hot-melt pressure-sensitive adhesive composition prepared in each example was heated and melted at approximately 100°C using an extruder and extruded onto a 25 μm-thick PET substrate to produce a pressure-sensitive adhesive sheet with a 50 μm-thick pressure-sensitive adhesive layer laminated to the PET substrate. The produced pressure-sensitive adhesive sheet was cut to a size of 10 mm wide and 100 mm long to prepare a sample for measuring holding power. At 23°C and 50% RH, the adhesive surface of the measurement sample was pressed against a Bakelite board (phenolic resin board) as an adherend, with a 10 mm wide and 20 mm long adhesion area, using a 2 kg roller to move back and forth once. The adherend with the measurement sample attached in this manner was then suspended in a 40°C environment with the length direction of the measurement sample aligned vertically and allowed to stand for 30 minutes. A 500 g load was then applied to the free end of the measurement sample, and the sample was left to stand with the load applied in a 40°C environment for 60 minutes, in accordance with JIS Z0237. After 60 minutes, the displacement distance [mm] from the initial attachment position of the measurement sample was measured. If the measurement sample had fallen off the Bakelite plate after 60 minutes, it was evaluated as "fallen." The measurement device used was a creep tester (model TG83-001) manufactured by Imada Seisakusho. The measurement results are shown in the corresponding columns in Tables 2 to 4.

[0103] [Shear viscosity measurement] The pressure-sensitive adhesive composition PL prepared in each example before the addition of the crosslinking agent was applied to a separator (Mitsubishi Chemical Corporation, product name MRF-38), dried, and peeled off from the separator to obtain a sheet piece approximately 50 μm thick. Multiple sheets obtained were stacked to produce a sheet slightly thicker than 0.5 mm, which was used as a sample for measuring shear viscosity. The shear viscosity [Pa·s] of the sample was measured using a ThermoFicher RheoStress 6000 rheometer under the following conditions: measurement temperature: 130°C, measurement speed: 0.1 (1 / sec), measurement gap: 0.5 mm, and measurement probe: P8 CSJ (measurement surface: Φ8 plate). The measurement results are shown in the corresponding columns in Tables 2 to 4.

[0104] [Table 2]

[0105] [Table 3]

[0106] [Table 4]

[0107] As is clear from the results shown in Table 2, in a system containing polymer A2 and polymer B1 as base polymers, the adhesive compositions of Examples 1 to 3, in which the content of polymer B1 in the base polymer is 10% by weight or more and 90% by weight or less, have lower shear viscosity than the adhesive composition of Comparative Example 1, in which the content of polymer B1 is 5% by weight, and are superior in one or both of adhesive strength and holding power compared to the adhesive composition of Comparative Example 2, in which the content of polymer B1 is 95% by weight.

[0108] The results shown in Tables 3 and 4 also showed similar trends. Specifically, in systems containing polymer A2 and polymer B2 as base polymers, the PSA compositions of Examples 4 and 5, in which the content of polymer B2 in the base polymer was 10 wt % or 50 wt %, had superior adhesive properties (adhesion strength and / or holding power) compared to the PSA composition of Comparative Example 3, in which the content of polymer B2 in the base polymer was 95 wt %. Furthermore, in systems containing polymer A1 and polymer B2 as base polymers, the PSA composition of Example 6, in which the content of polymer B2 in the base polymer was 10 wt %, had a lower shear viscosity and superior holding power compared to the PSA composition of Comparative Example 4, in which the content of polymer B2 was 5 wt %, and had superior adhesive properties (adhesion strength and / or holding power) compared to the PSA composition of Comparative Example 5, in which the content of polymer A1 was 5 wt %. The shear viscosities of the PSA compositions of Examples 1 to 6 were all within a range suitable for use in extrusion molding. On the other hand, the PSA compositions of Comparative Examples 3 and 5 suffered cohesive failure of the adhesive layer during adhesion measurement.

[0109] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. [Explanation of symbols]

[0110] 1,2 Adhesive sheet 21 adhesive layer 21A First adhesive side 21B Second adhesive surface 31,32 Release liner

Claims

1. A hot melt pressure-sensitive adhesive composition comprising a base polymer, the base polymer consists of only an acrylic polymer A and an acrylic polymer B, wherein the acrylic polymer A is a polymer of monomer components containing more than 50% by weight of a (meth)acrylic monomer A having an alkyl group having from 4 to 8 carbon atoms, and containing 0.01% by weight or more and 15% by weight or less of a functional group-containing monomer selected from a carboxy group-containing monomer and a hydroxy group-containing monomer, the acrylic polymer B is a polymer of monomer components containing more than 50% by weight of a (meth)acrylic monomer B having an alkyl group having from 9 to 12 carbon atoms, and containing from 0.01% by weight to 15% by weight of a functional group-containing monomer selected from a carboxy group-containing monomer and a hydroxy group-containing monomer, the content of the acrylic polymer B in the base polymer is 10% by weight or more and 90% by weight or less when the total amount of the acrylic polymer A and the acrylic polymer B in the base polymer is taken as 100% by weight, The hot melt pressure-sensitive adhesive composition further comprises a crosslinking agent.

2. The weight average molecular weight of the acrylic polymer A is 75×10 ４ Above 120 x 10 ４ is as follows: The weight average molecular weight of the acrylic polymer B is 75×10 ４ Above 120 x 10 ４ The hot melt pressure-sensitive adhesive composition according to claim 1, wherein:

3. 3. The hot melt pressure-sensitive adhesive composition according to claim 1, which has a shear viscosity at 130°C of 7000 Pa·s or less.

4. The hot melt pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the crosslinking agent is an isocyanate-based crosslinking agent.

5. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed using the hot melt pressure-sensitive adhesive composition according to claim 1 .

Images